Morphological and genetic characterization of the first Isospora species (I. lugensae n. sp.) from a Kerguelen petrel (Lugensa brevirostris)

• Published in: Parasitology research (1987) 2021-03, Vol.120 (3), p.1037-1047
• Main Authors: Yang, Rongchang, Brice, Belinda, Liu, Qier, Berto, Bruno P, Austen, Jill, Ryan, Una M
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Biomedicine; Fossils; Genomes; Genomic analysis; Homology; Immunology; Lugensa brevirostris; Medical Microbiology; Microbiology; Mitochondrial DNA; Morphology; New species; Oocysts; Parasites; Phylogeny; Protozoology - Original Paper; Ribonucleic acid; RNA; Spherules; Sporocysts; Sporozoites; Transfer RNA
• ISSN: 0932-0113; 1432-1955
• DOI: 10.1007/s00436-021-07046-6

A new coccidian species, Isospora lugensae n. sp., was described from a single Kerguelen petrel ( Lugensa brevirostris ). Sporulated oocysts ( n  = 25) were characterized as subspheroidal to ellipsoidal measuring 24–25 μm × 21–23 μm (24.8 × 22.2 μm) in length/width (L/W), respectively, with a ratio of 1.07–1.14 μm (1.12). They contained a bi-layered wall with a thickness of 0.8–1.2 μm (1.0) and the outer layer smooth, with c.2/3 of total thickness. The oocyst contained two polar granules with both micropyle and oocyst residuum absent. Ovoidal sporocysts ( n  = 25) measured 15–16 μm × 10–11 μm (15.7 × 10.8 μm) in L/W, with a ratio of 1.41–1.49 μm (1.46). A flattened to knob-like Stieda body was present ( c. 0.5 μm deep × 2.5 μm wide) as well as a rounded to trapezoidal sub-Stieda ( c. 1.5 μm deep × 3.0 μm wide); however, no para-Stieda body was detected. The sporocyst residuum was composed of scattered spherules of different sizes, while vermiform sporozoites contained a refractile body, nucleus and visible striations. Analysis of the full-length mitochrondrial (mtDNA) genome revealed 3 protein-coding genes, (CytB, COI and COIII), 18 LSU and 14 small subunit (SSU) rDNA fragments, without transfer RNA genes with a total length of 6257 bp. Phylogenetic analysis of genomic SSU ribosomal sequences indicated that Isospora lugensae n. sp. is genetically similar to Eimeria reichenowi , isolated from a red-crowned crane ( Grus japonensis ) from Japan, with a 96.6% homology. The mtDNA sequence is most similar to Isospora serinuse with a 95.8% genetic similarity. Based on morphological and molecular data, this isolate is a new species of coccidian parasite that to date has only been found in a Kerguelen petrel.